This issue has been completely fixed since Plesk 11.0.9 MU#47.
An attempt to update Plesk fails with the following message:
Exception: Failed to solve dependencies:
1:perl-Digest-SHA-5.47-127.el6.x86_64 requires perl = 4:5.10.1-127.el6
The problem is caused by an error in Plesk packages' dependency definitions.
The problem will be fixed in a future update to Parallels Plesk Panel.
In order to install updates, first update Perl using
yum update perl
Then run the Plesk update again using the instructions provided in Knowledgebase article #9294.